Unusual clots have been detected in the brains of a few people after they were injected with the Oxford-AstraZeneca vaccine.
These “cerebral venous sinus thromboses (CVSTs)” have led for some countries, including Germany, France and Canada, to restrict who can receive the injection.
The World Health Organization (WHO) and the European Medicines Agency (EMA) English) say the benefits of the vaccine outweigh any risks.
Scientists and drug safety regulators around the world are trying to find out if the vaccine is actually causing these strokes , how great the risk could be and what it could mean for vaccination programs.
Is the vaccine causing blood clots ?
At the moment, we do not know.
The EMA, which has been reviewing the security data, says that “it is not proven, but it is possible. ”
The organization has to find out if the reported clots are a side effect or a coincidence that would have occurred naturally.
This is incredibly difficult when it comes to rare events. If, on the other hand, one of each 10. 000 people had severe blood clots, the answer would be obvious.
I have spoken with respected scientists: some of them are skeptical, others are increasingly convinced.
Some point to the highly unusual nature of clots as a sign that something might be happening.
Often appear together with low levels of platelets in the blood, which are one of the main components of a clot, and with antibodies related to other bleeding disorders that appear in the blood.
Others say that there is insufficient evidence and that the reported cases could be due to to covid – 19, which in turn is related to abnormal clotting.
How great could the risk be?
It is still entirely possible that the risk is zero, as vaccines have not been shown to cause brain clots.
The Paul Ehrlich Institute in Germany reported 31 cerebral venous sinus thrombosis and nine deaths among the 2.7 million vaccinated there.
However, the most recent data from the UK report far fewer clots, only five, despite having vaccinated many more people: 11 million.
The European Medicines Agency, which has evaluated data from around the world, estimates that the risk of CVST is around one in 100. 000 in people under 60 years they have received the AstraZeneca vaccine.
It is “more than we would expect to see,” said the organization’s head of safety monitoring, Dr. Peter Arlett.
However, it is not clear what the incidence rate of these blood clots in the brain really is.
Estimates vary from around two cases per million people every year to almost 16 per million in normal times, and the coronavirus itself may also be causing them.
Why is there a difference between the UK and Germany?
You could expect to see the same number of CVTS in different countries if they were actually caused by the vaccine.
However, the UK and Germany have vastly different figures .
An argument is that the profile of the people who get vaccinated is different.
Kingdom Kingdom started to vaccinate from the oldest age groups, while Germany was one of the countries that initially refused to use the vaccine in those older than 65 years due to lack of data in the trials.
In contrast, it is believed that almost the 65% of Germans who received AstraZeneca have less than 60 years.
Side effects in general tend to be more serious in younger people, since they have a stronger immune response.
That is one of the reasons that is considered to explain that the United Kingdom has had fewer cases.
However, CVSTs are inherently more common in younger women and taking the pill increases the risk.
Therefore, natural risk levels, whether women pe If people are vaccinated or not, they could also play a role.
Separating all of this is challenging, but the EMA indicated that it had found no specific risk factors such as age, gender or medical history.
Is the AstraZeneca vaccine safe?
Nothing in medicine is completely safe and even highly toxic therapies are used in certain circumstances.
Chemotherapy drugs have brutal side effects, but they are very valuable.
And even over-the-counter pain relievers like acetaminophen and ibuprofen have serious side effects, although incredibly rare.
The real decision is always if the benefits outweigh the risks.
This is a particularly great challenge in a pandemic. Normally, medicine would be based on the “precautionary principle” to demonstrate adequate safety before administering a new medicine to large numbers of people.
But in a pandemic, any delay in vaccination of populations will also cost lives.
Based on data from Germany alone, of the 1 million vaccinated people, it would be expected that 12 had a blood clot and four of them died.
But if a million people of 60 years will contract the coronavirus, around 20. 10 would die of covid – .
In that line, if a million people of 40 years were infected with the coronavirus, they would die about 1. 000. And in the case of the people of 30 years there would be a few hundred deaths.
Vaccination benefits clearly increase with age and countries such as Germany and Canada have allowed the AstraZeneca vaccine to be used in larger population groups
These decisions will also depend on which alternative vaccines are available and who remains to be immunized.
The world is examining the data carefully, but still it will take time to have a clear answer.
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